Multi-legged equipment support for cameras, spotting telescopes and the like and jam-plate lock for same

ABSTRACT

A multi-leg equipment stand has a unitary user interface. All legs can be adjusted simultaneously, or, an individual leg can be adjusted, by distinct motions of the interface. A collar is near to an equipment support shoulder. Rotation around a vertical axis releases all legs. For a tripod, tilting the collar in one direction releases only one of three legs. The tilt may be toward the leg to be moved. The legs have adjacent, telescoping components. A control rod extends from the collar, through the hollow interior of the upper component, to a jam-plate, at the lower end of the upper component. The plate jams between an inside of the lower component, and an inside of the upper component. The rod passes through the jam-plate. Pushing the rod tilts the jam-plate, freeing it from jamming. A spring returns it to jamming if released. For each leg, the collar underside has a two level cam recess. The rods each have a cam follower surface at their shoulder end. Rotating the collar pushes each of the rods, releasing all jam-plates. Returning the collar allows the rods to move back, under influence of springs. Tilting the collar in any one of the leg directions pushes only one of the rods, tilting and releasing one jam-plate. The rod and jam-plate may be used with a single leg. The user interface can be used with two or more legs. The jam-plate may lock against a bushing, rather than directly against the upper component. Rather than rods that are pushed, cables can be pulled. Three component legs can also be activated using jam-plates.

CROSS-REFERENCE OF RELATED APPLICATIONS

This is a 35 U.S.C. § 371 national stage of co-pending internationalapplication PCT/US02/14714, filed on 9 May 2002, which itself claimspriority and the benefit of the filing date under 35 U.S.C. 119(e) toU.S. Provisional application No. 60/290,002, which was filed on 10 May2001. The benefit of the filing date of co-pending internationalapplication PCT/US02/14714 is also claimed under 35 U.S.C. § 120.

SUMMARY

One invention disclosed herein is a multi-legged equipment stand. Itcomprises a shoulder bracket and coupled to the shoulder bracket, aplurality of telescoping, elongated legs. Each leg has an uppermostelongated component and a lower elongated component. The uppermost andlower components are elongated along an axis of elongation, theuppermost elongated component being translationally fixed relative tothe shoulder bracket. The lower elongated component is translatablerelative to the shoulder bracket and the uppermost component, along theaxis of elongation. The uppermost component has a shoulder end, and aground end, as does the lower component. The shoulder end of theuppermost and lower components are located nearer to the shoulderbracket than the ground end of the respective components. For each pairof uppermost and lower components of a leg, a releasable lock engagesboth the uppermost and lower components. The lock is movable from alocking configuration, which contacts both of the uppermost and lowercomponents, to a nonlocking configuration, in which the components aremovable relative to each other under the influence of a force less thanthe force of gravity applied to the lower component. Coupled to each ofthe lock mechanisms, is a control rod, which extends from the lockplate, along the uppermost elongated component to adjacent the shoulderbracket, terminating in a cam follower surface. The rod is coupled tothe lock mechanism to selectively lock or unlock the lock mechanism ifthe control rod is moved. There is also a user interface collar,supported by the shoulder bracket, adjacent the cam follower surfaces ofthe plurality of control rods. The collar comprises, for each of thecontrol surfaces, a mating cam recess surface. There is a couple betweenthe shoulder bracket and the user interface collar, which partiallyrestrains the collar such that: a unified control motion of the collarrelative to the support simultaneously moves all of the control rods sothat all of the lower components are free to translate relative to therespective uppermost components; and a first single control motion ofthe collar relative to the shoulder bracket moves only a first one ofthe control rods so that a corresponding one of the lower components isfree to translate relative to its respective uppermost component, whilesimultaneously, all others of the lower components are unaffected withrespect to translating relative to their respective uppermostcomponents. The collar is further restrained such that a second singlecontrol motion of the collar relative to the shoulder bracket moves onlya different, second one of the control rods so that a corresponding oneof the lower components is free to translate relative to the respectiveuppermost component, while simultaneously, all others of the lowercomponents are unaffected with respect to translating relative to theirrespective uppermost components.

The number of legs can be two, three, or more.

The lock mechanism can be a spring-loaded jam-plate. If so, theuppermost and lower elongated leg components are hollow tubes, with thelower component arranged concentric with and outside of the uppermostcomponent. The jamplate is arranged to jam against an inner surface ofthe lower elongated component and against the uppermost elongatedcomponent. More specifically, the jam-plate is arranged to apply a forcethat has a radially outward component against each of an inner surfaceof the uppermost leg component and an inner surface of the lower legcomponent. The jam-plate can press directly against an inner surface ofthe uppermost elongated component, typically an extended portionthereof. Alternatively, the stand can include a bushing fixed to theground end of the uppermost leg component. The jam-plate is arranged tojam against the uppermost elongated component by jamming against thebushing.

In an advantageous embodiment, the uppermost and lower elongated legcomponents comprise hollow tubes, with the lower component arrangedconcentric with and outside of the uppermost component, the control rodcomprising a rod that passes along the inside of both the uppermost andlower hollow tube components.

Of the control motions, in one embodiment, the user interface collarcomprising a collar, the unified control motion comprising rotationaround a unified control axis, the first single control motioncomprising tilt around a first, single control axis and the secondsingle control motion comprising tilt around a second, single controlaxis. The single control axes may lie in a plane that is perpendicularto the unified control axis.

There are various forms that the collar can assume. The collar can have,for each control rod, a cam recess surface shaped to simultaneouslyforce each of the control rods away from the collar if the collar isrotated around the unified control axis, and, individually, force asingle control rod away from the collar if the collar is tilted around asingle control axis associated with the respective single control rod.In one embodiment, the cam recess surfaces comprise a two level well,with a sloped region joining the two levels. Or the cam profile can be acontinuous 360° wave profile having at least two levels, as describedabove, in a repeating pattern around the circumference of the usercontrol element.

The leg components can have various shapes, including circularcylindrical, square tubes, triangular tubes, etc. If the legs componentsare circular cylinders, then an advantageous shape for the jamplate isone having at least one arcuate curved edge, for instance, a portion ofan oval, or ellipse, or other curved shape. If a busing is used, thenthe jam-plate may have an arcuate edge, opposite a straight edge.

An exemplary user interface for a tripod is a three-lobed unitarycollar, which controls both unified motion of the control rods, andindividual motion of the control rods. The unified control motion maysubstantially simultaneously force the control rods toward the groundends of the legs, or, alternatively, their shoulder ends. Similarly, thesingle control motion may force the respective control rod toward theground end of the legs, or the shoulder end.

Another invention disclosed herein is similar to that described above,but, rather than a control rod, other control linkages can be used, suchas a tension bearing cable, or a network of links. In such a case, thecontrol member extends from the lock mechanism to the user interfacecollar, and terminates in a control component. Adjacent the controlcomponents of the plurality of control members, the collar has, for eachof the control components, a control activation element. The controlmember is coupled to the lock mechanism to selectively lock or unlockthe lock mechanism if the control mechanism is moved. The collar iscoupled to the support, similar to that as described above, so that aunified control motion of the collar simultaneously moves all of thecontrol members so that all of the lower components are free totranslate relative to the respective uppermost components, and differentsingle control motions of the collar move only an individual one of thecontrol members so that a corresponding one of the lower components isfree to translate relative to its respective uppermost component, whilesimultaneously, all others of the lower components are unaffected withrespect to translating relative to their respective uppermostcomponents.

There is also disclosed an equipment stand comprising at least threetelescoping legs. Each leg has at least two telescoping components. Asingle, unitary control user contact member is operative to selectivelyperform one of the following release functions: release all of the legsfor telescoping adjustment between the at least two telescopingcomponents; and release only a selected one of the legs for telescopingadjustment between the at least two telescoping components of the oneleg, while, simultaneously maintaining all others of the legs lockedagainst adjustment between the at least two telescoping components ofthe other legs.

A typical version of such a stand is a tripod. The stand my havetelescoping, cylindrical leg tubes. The tubes may be circular cylinders.

This variation may have, for each leg, a lock mechanism and a controllinkage. The lock mechanism is operative to selectively lock the twotelescoping components against relative motion, and to free them forrelative motion. The control linkage is arranged to couple the lockmechanism to the user contact member.

The unitary control user contact member may comprise a collar, that isrotatable around a unified motion axis to release all of the legs fortelescoping adjustment.

The collar may be further tiltable around: a first single motion axis torelease a first of the legs for telescoping adjustment; a second singlemotion axis to release a second of the legs for telescoping adjustment;and; a third single motion axis to release a third of the legs fortelescoping adjustment.

The first, second and third single motion axes may all intersect at asingle point. Alternatively, the first and second single motion axes mayintersecting at a first intersection point, the second and third singlemotion axes may intersect at a second intersection point, and the thirdand first single motion axes intersecting at a third intersection point,the first, second and third intersection points forming vertices of atriangle having a centroid through which the unified motion axis runs.

Still another invention is a locking telescoping leg mechanism. Itcomprises an uppermost elongated hollow tubular leg component, having aninside surface and an outside surface; and a lower elongated legcomponent, having an inside surface and an outside surface. Theuppermost and lower components are elongated. The uppermost and lowerelongated leg components are translatable relative to each other, alongthe axis of elongation. The uppermost component has a shoulder end, anda ground end. The lower component has a shoulder end and a ground end,with the shoulder end of the lower component being located nearer to theshoulder end of the uppermost component than is the ground end of thelower component. A releasable lock plate engages both the uppermost andlower components. The jamplate is movable between: a lockingconfiguration and an unlocking configuration. In the lockingconfiguration, it applies a radially outward force to the inside surfaceof the uppermost component and the inside surface of the lowercomponent. In the unlocking configuration, at least one of the radialoutward forces is small enough so that the components are movablerelative to each other under the influence of a force less than theforce of gravity applied to the lower component. Coupled to thejam-plate is a control member, which extends from the jamplate, insidethe uppermost elongated component through substantially its entirelength, to adjacent the shoulder end, terminating in a shoulder end. Thecontrol member is coupled to the lock plate such that motion of thecontrol member moves the lock plate from the locking configuration tothe nonlocking configuration.

There may be a spring that forces the control member toward a restposition, which corresponds to the locking configuration of the lockplate. The lock plate may be arranged to provide a force directly to theupper leg component, or, indirectly, for instance, through a bushing.There may be a jam-plate support that has a surface with a slot, and thejam-plate then is a plate having an edge that is sized and shaped to fitinto the slot.

The jam-plate is arranged such that in the locking configuration, itconstitutes a portion of a continuous force path from the lowerelongated leg component to the upper elongated leg component, and in thenon-locking configuration, the jam-plate is moved such that the forcepath from the lower elongated leg component to the upper elongated legcomponent is discontinuous at the jam-plate.

The inventions disclosed herein will be understood with regard to thefollowing description, appended claims and accompanying drawings, where:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross sectional view of a single telescoping leg,with internal jam-plate and control rod, with adjacent components shownin a relatively collapsed relation;

FIG. 1B is a schematic cross sectional view of a single telescoping legshown in FIG. 1A, with adjacent components, shown in a relativelyextended relation as compared to that shown in FIG. 1A;

FIG. 1C is a schematic cross sectional view of a single telescoping legsimilar to that shown in FIG. 1A, but without a jam-plate supportbushing;

FIG. 2 is a schematic three dimensional rendition of a portion of atripod incorporating a unitary user interface control collar and acontrol rod, shown extending from the user interface to within a leg;

FIG. 3 shows a schematic three dimensional rendition of the tripod shownin FIG. 2, from below the user interface control collar, illustrating acam follower surface of a control rod engaging a profiled cam recesssurface of a control collar;

FIG. 4A shows schematically a user interface control collar from below,in a slightly inclined orientation;

FIG. 4B shows schematically the user interface control collar shown inFIG. 4B, directly from below, in a plan view;

FIG. 4C shows, schematically in partial cross-section, an edge of alobe, cut along lines CC, shown in FIG. 4A, through a cam recess;

FIG. 4D shows, schematically, a recess in cross-section as shown in FIG.4C, with a control rod extending into a deep region of a recess;

FIG. 4E shows, schematically, a recess in cross-section as shown in FIG.4C, with a control rod extending into a shallow region of a recess;

FIG. 4F shows, schematically, a recess profile in the form of acontinuous wave, for use with a user control collar that can be rotatedcontinuously in one direction;

FIG. 5 shows schematically the user interface control collar shown inFIG. 4A, from above, in a slightly inclined orientation;

FIG. 5A shows schematically the user interface control collar shown inFIG. 5, from direction A, in a side view;

FIG. 5B shows schematically the user interface control collar shown inFIG. 5, from directly above, in a plan view;

FIG. 5C shows schematically the user interface control collar shown inFIG. 5, from direction C, in a side view;

FIG. 6 shows, schematically, an end view of three leg tubes and theirrespective jam-plates;

FIG. 6A shows, schematically, an end view of a single leg tube with itsjam-plate in an unlocked orientation;

FIG. 6B shows, schematically, an end view of a variation of a reducedsize jam-plate, with lateral edges removed;

FIG. 6C shows, schematically, an end view of a single leg tube without ajam-plate support bushing;

FIG. 7 shows, schematically, in cross-section, a dual jam-platearrangement for a three component leg;

FIG. 8 shows, schematically, in perspective view, a jam-plate that has atab, and a bushing support for use therewith;

FIG. 9A shows, schematically, in a cross-sectional view, a jam-plate andsupport as shown in FIG. 8, along lines 9—9, in use to lock two adjacenttube components of a leg, in a locking configuration;

FIG. 9B shows, schematically, in a cross-sectional view, the jam-plateand support as shown in FIG. 9A, in a non-locking configuration;

FIG. 10A shows, schematically, in an elevation view view, a relativelylarge volume user control collar;

FIG. 10B shows in a top plan view the large volume collar of FIG. 10A;

FIG. 11 shows, schematically in a perspective view, a jam-plate that canbe hinged to a support bushing;

FIG. 11A shows, schematically, in a cross-sectional view, a hingedjam-plate as shown in FIG. 11, as cut along lines A—A, fixed to asupport bushing, also in cross-section;

FIG. 11B shows, schematically, in a perspective view, a jam-plate thatincludes a living hinge.

DETAILED DESCRIPTION

The inventions disclosed herein relate to portable stabilizationdevices, such as monopods and tripods, typically used for spottingscopes, cameras, video cameras, telescopes, etc. There are at least twomajor aspects to these inventions, and several other ones. A first majoraspect relates to mechanism within a single leg that permits it to belocked. The second major aspect relates to a user interface to control aleg locking mechanism in general, and, in particular, the mechanismdisclosed. The first aspect (described below as “jam-plates”) may beused in connection with a single leg device, such as a monopod, as wellas multiple leg devices, such as tripods, or, if practical, two or fourleg devices. The second aspect, described below as a “user interface,”is only applicable to devices with two or more legs.

Portable tripods can be collapsed into a small volume for easytransportation, and then deployed to full size (approximately humanheight) when required. The practical method for accomplishing suchcollapsibility is to construct each leg in multiple, nested, telescopingsegments.

Many uses of monopod and tripod supported devices require rapid setupand stabilization (deployment) as well as rapid return to the collapsedstate (packing). Using bird watching as an illustrative, non-limitingexample, the user needs to quickly focus and stabilize a spottingtelescope onto a bird before the bird escapes from view. In addition,the user needs to be able to collapse the tripod quickly to enable rapidrelocation to the next spotting site. In addition, users need to be ableto quickly adjust the length of individual monopod and tripod legs toaccommodate uneven terrain, thereby allowing a tripod to stand erect andstable.

The majority of known monopods and tripods have segmented, nestedtelescoping legs with an external clamping mechanisms to fix each pairof adjacent segments to one another, creating a leg of adjustablelength. For a three-segment leg, the user must generally perform twoextension operations for each of the three legs, for a total of sixoperations. The user must then use both hands to manually adjust thelengths of individual legs to accommodate uneven terrain. For instance,a knurled ring around the outside of the leg must be tightened.Sometimes, such a ring is hard to release and rotate. These operationstake an excessive amount of time, and therefore reduce the success andenjoyment of a bird-watching session.

Thus, such a conventional tripod has numerous problems including, atleast, the following. Multiple manual operations are required to extendor collapse a single leg. Two hands are required when making adjustmentsin the length of an individual leg. An excessive amount of time isrequired to perform the aforementioned operations. Individual legs mustbe extended, or collapsed, individually. Also, sometimes excessive forceand/or torque is necessary to ensure that the knobs/levers are tightenough to restrict movement on conventional tripods.

Basic Jam-plate and Control Rod Configuration. FIG. 1A shows,schematically, a portion of a leg with an internal jam-plate, incross-section. (As used herein and in the claims, jam-plate andlock-plate are synonymous.) The leg 10 is generally elongated along thedimension indicated by the arrow E. It has a lower leg component 12 andan upper leg component 14. The lower component 12 typically has acircular cylinder as a crosssection along a plane that is perpendicularto the dimension E of elongation. (The crosssection can also be otherregular shapes, such as a square, rectangle, or other shapes in which ajamplate, described below, can work as a lock.) In the embodiment shown,the lower component 12 has an inner diameter D_(li) that is larger thanthe outer diameter D_(uo) of the upper component (although this relationmay be reversed). This is useful for applications where the equipmentsupport is used in wet or watery conditions. If so used, the lower legcan be placed in water that is almost as deep as its upper support end16, without risk of dragging water and debris from the wet environmentinto the space between the lower component 12 and adjacent component 14,when the two legs are collapsed together. (This feature alone is notnew, nor is it claimed alone. It is mentioned merely to ensure clarity.)An end cap 18 completes the protection from a wet support environment,and also provides favorable friction conditions.

To aid in description, the designations “upper” and “lower” have beenassigned to the portions of the legs that would typically be so orientedif the leg is used with its “lower” end resting on the ground, or someother grounded support, and the leg supports the weight of theinstrument that it supports, by compression. This is the mode in whichthe equipment support would most frequently be used. However, thegeneral inventions described herein, can also be used if the leg or legsof the equipment support are anchored to an overhead fixture, forinstance by clamps, or other tension bearing couple, and the equipmenthangs below. Such an orientation would be extremely rare, but, it iscontemplated as a possible use for the inventions disclosed. In such anapplication, “upper” would actually mean “lower” and vice-versa.

An annular bushing 2 of a low friction material is fixed to the upperend of the lower tube 12 and slides around the outside of the upper tube14. It provides a favorable sliding pair arrangement that is rather easyto fabricate. In addition, the support bushing 26 has an annular portion7 that also provides a sliding bearing, against which lower component 12slides. Further, the lower 12 and upper 14 components have relativeinner diameter D_(li) and outer diameter D_(uo) that are sized, withenough clearance therebetween, such that any friction that arisestherebetween is so small that when the two nested components are heldwith their dimension of elongation E aligned with the action of theforce of gravity, and the upper component is retained againsttranslation, the force of gravity is sufficient to cause the lowercomponent to move at a speed that is great enough to be convenient forunassisted extension of the tubes. Typically, this would result in fulldeployment of a pair of adjacent tubes in less than one second. Theremay also be damping provided, as described below.

A control rod 20 extends the full length of the upper component 14, and,slightly beyond at both the lower end 22 and the upper end 24. Thecontrol rod 20 is located within the interior of the upper component 14by means of a lower 26 and upper 28 bushing, each of which have holesthrough which the control rod passes. Note that the control rod 20 neednot be concentric with the upper component 14 (or the lower component12). In fact, it is preferable that the location be eccentric, notconcentric, because eccentricity facilitates tipping the jam-plate asdescribed below. (For embodiments with more than two adjacentcomponents, this lack of concentricity is exploited further, asexplained below.) Further, to facilitate tipping of the jam-plate, ahole 31 is a slightly elongated slot, elongated in the direction acrossthe diameter of the tube components shown in cross-section, and also asshown in FIG. 6. The length of the hole must be sufficient to allow theplate to tilt, but not so long that the plate is too loose in theunlocked position. It has been found that, in general, a length equal toabout 2–3 diameters of the control rod 20 is appropriate.

The control rod 20 terminates in a stop 30, such as a nut or stampedend, or other equivalent stopper. The stopper retains a jam-plate 32from slipping off from the end of the control rod. The stop 30 alsopushes the jam-plate 32 into the locking configuration, as the spring 40pushes the control rod 20 and the jam-plate toward the upper component12, as explained below. An actuation nut 34 (or equivalent stopper)actuates the jam-plate in the downward direction, as discussed below, torelease the lock. The lower support bushing 26 has a channel 36therethrough with an enlarged diameter relief 38 at the lower end toallow the actuation nut 34 to fit within it. A return spring 40, forexample, a coil spring, is trapped between the support bushing 26 and aspring stop 42. The return spring returns the control rod to a restposition, which, in the embodiment shown, corresponds to a lockingconfiguration. A travel stop 5, such as a screw or pin aids inpreventing the upper and lower components from being pulled totallyapart from each other.

FIG. 6 shows, schematically, the geometry of the jam-plate and thebushing and the lower component, in a locked configuration. FIG. 6Ashows the corresponding geometry for an unlocked configuration. Thejam-plate 32 is sized to fit roughly between an inside surface of thelower component 12 and an inner surface 46 of a cut away end portion 48of the lower support bushing 26. The size is such that the extent of theportion of the jam-plate 32 aligned roughly along the dimension from thesurface 46 of the bushing, toward the inner surface 44 of the lowercomponent 12, indicated by the arrow L in FIG. 6, is longer than thedistance between the surface 46 and the inner surface 44 along thatdimension. In the embodiment shown, the shape of the space is straightat one end, and curved at the other, roughly a portion 52 of a circle,or an oval, or an ellipse, with one end 50 cut off, at a chord. Theshape of the jam-plate 32 is approximately congruent, but the distancefrom the chord 50 to the apex of the curve of the arc 52 is longer thanthe corresponding distance of the open space.

Operation of Jam-Plate. The operation of the jam lock is as follows.FIG.1A and FIG. 6 show the lock in a locking configuration. It is locked,because the jam-plate presses against both the support bushing 26, andagainst the inner surface 44 of the lower leg component 12. The supportbushing 26 is fixed to the lower end 22 of the upper leg component 14.Any force that would act to collapse the upper and lower componentstoward each other also tends to force the jam-plate into a position thatis more closely perpendicular to the axis E. This also tends to increasethe jamming force, and to resist collapse of the leg components.

If the user desires to unlock and re-configure the components, the userpushes the control rod 20 (by means described below) toward the groundend of the legs along the direction of the arrow B. (The various meansby which the rod may be pushed is discussed below.) The configuration ofthe jam-plate and rod in an unlocked configuration is shown in part inFIG. 1B. The stop 34 causes the jam-plate 32 to change its orientationrelative to the axis E of elongation, and thus, to the opening insidethe space between the inside corner 46 of the lower bushing 26 and theinside wall 44 of the lower component 12. This unlocked configuration isalso shown in FIG. 6A. Basically, the plane of the jam-plate becomesmore parallel to the axis of elongation E, and thus, the projection ofits length along the dimension L, onto a plane that is perpendicular tothe dimension of elongation E of the legs, becomes smaller. In otherwords, the jam-plate tilts and no longer jams against the supportbushing 26 and the interior 44 of the lower component 12 at both itsends 50, 52.

With the jam-plate no longer jamming against these components, there isno longer enough force between them to resist relative motiontherebetween, in either the collapsing or extending directions.Typically, as mentioned above, they will move relative to each othersimply under the force of gravity applied to either the upper or lowerleg component 14 or 12, while the other component is held stationary.

In general, the jam-plate operates by providing a force path between theupper component 14 and the lower component 12, which results in a forcebeing applied to both. The force that is applied to each, has acomponent that is radially outward with respect to the respective legcomponents. This radially outward force applied to each component alsogives rise to a frictional component that is normal to the radiallyoutward force. The frictional force opposes collapse of the legcomponents together. Further, as the leg components are pushed towardeach other, that tends to tilt the jam-plate more toward the lockingconfiguration, thereby increasing the radial, and the normal forces, andthus, further resisting collapse of the components together. (By“radially outward,” it is meant generally from an inner region, such asa central axis outward toward the perimeter wall of the leg component.In this discussion, “radially” is being used loosely, and is not meantto be limited to precisely along a radius, from a center.)

There are known devices where a jamming force operates radially inwardupon a wall of an inner tube, and radially outward on a wall of an outertube. For instance, there are mechanisms where a wedge is forced betweenfacing faces of nesting tubes: i.e., between the outer face of an innertube and the inner face of an outer tube. There are also devices where ajamming force is applied between an outer surface of a tube, and acollar that surrounds the tube.

Thus, by pushing the control rod 20, the locking mechanism isdisengaged, to allow either extension of the leg components away fromeach other, or compression of the leg components toward each other, to acompressed configuration. By releasing the control rod to return to itsrest position relative to the upper component 14, under influence of thespring 40, the jam-plate 32 again returns to its orientation shown inFIG. 1A and FIG. 6, that is closer to perpendicular to the axis ofelongation E, and thus jams between the corner 46 of the lower bushing26 and the inner wall 44 of the lower component 12. Thus, the lower 12and upper 14 leg components are again locked against relativetranslation.

An advantageous feature of the jam-plate 32 is that an increase in theload (more pressure applied to the legs, such as by the operator leaningon the upper portion of a leg) causes the jamming force to increase.Thus, the leg support function is not prone to failure under anincreasing load.

Other Shapes for Jam-plate. As shown in FIG. 6, each individualjam-plate 32 may be substantially congruent with the space in which itresides, but is a little bit larger than the space, at least along thedimension L. However, this need not be the case. For instance, as shownin FIG. 6B, the lateral edges 33 and 35 of the jam-plate can beeliminated, such that the modified jam-plate 62 has only a centralportion, bounded by spaces 53 and 55 between the inner walls 44 of thetube. This variation may be useful for very lightweight models, or tosimplify some aspects of manufacture. On the other hand, it might bemore prone to undesired jamming, or failure to jam when desired, as thejam-plate may be more prone to twist around the long axis of the controlrod, due to the abundant clearance.

In general, the jam-plate and its support must provide a force path fromone leg component to an adjacent leg component. For the inventionsdescribed herein, the force is ultimately applied to each leg componentin a generally radially outward direction, thereby giving rise to anormal friction force that opposes translation of the leg components.The force may be applied from the jam-plate to each component by directcontact with each, (FIG. 1C), by contact with a support bushing that isfixed to the component (FIG. 1A, FIG. 9A (tabbed jam-plate), FIG. 11A(hinged jam-plate)), or, through a pivot that is fixed to the othercomponent, either directly, or, through a bushing or other support (FIG.7 (three component leg)). Each of these variations is discussed below.It will be noted that in most cases, it is helpful that the jam-platepivot around a fixed point, such as in internal corner of a supportbushing. However, this is not absolutely required. The pivot point maybe at an edge of a jam-plate, as shown in FIG. 1A, or, along its length,as shown in FIG. 9A.

FIG. 8 shows a part of a useful embodiment. In this embodiment, thejam-plate 332 has an arcuate edge 352 and a tabbed edge 350. The tab ofthe edge 350 fits into a slot 345 in a corner 346 of a slotted jam-platesupport bushing 326. As shown in FIG. 9A, which is a cross-section of ajam-plate 332 and support bushing 326 as shown in FIG. 8, incorporatedinto a two component joint in a leg, the support bushing 326 fits intoan upper end of a lower leg 314, in the same manner as described above.The jam-plate 332 is carried by and controlled by a control rod 320,similar to that described above. An end nut 330 urges the arcuate edge352 of the jam-plate 332 to jam against the inner wall 344 of the lowercomponent 312, under action of the return spring 340. The tabbed edge350 of the jam-plate is urged to press against the face 343 of thesupport bushing 326 (shown in FIG. 8, but not visible in the sectionshown in FIG. 9A). This, in turn, forces the support bushing 326 againstthe inner wall of the upper tube 314, thereby completing the force pathand resulting in a jamming force that prevents the components 312 and314 from collapsing toward each other when the plate 332 is in thejamming orientation. The circumferential portion 307 of the supportbushing 326 also serves as a sliding bearing between the busing 326 (andthus, the upper leg component 314, to which it is fixed) and the lowerleg component 312.

FIG. 9B shows the same elements as the control rod 320 is pusheddownward, in the direction of the arrow B. The jam-plate edge 352 islifted away from the inside wall of the lower component 312, and thejamming force ceases, permitting relative translation of the two legcomponents. It can be observed that the jam-plate 332 pivots around thecorner of the face 343, that borders the slot 345. It will also beunderstood that the tabbed edge 350 and the slot 345 cooperate to ensurethat the jam-plate stays in the proper location, as it is pusheddownward (in the direction of the arrow B) by the control rod. This mayadd some stability to the system, which is not present in the embodimentshown in FIG. 1A where the jam-plate is simply forced into the corner 46of the support bushing 26. It may be that the tolerances required forthe tabbed and slotted embodiment shown in FIG. 9A are not as stringentas those required for the un-tabbed embodiment shown in FIG. 1A.

As shown in FIG. 8, the slot 345 does not extend the entire width of thesupport bushing 326. However, a similar embodiment is for the slot toextend the entire width, leaving an overhanging portion of the face 343,above a wide opening. In that case, the edge 350 of the jam-plate 352need not be tabbed, and, rather, can be straight across. The function issomewhat similar, with slightly less security along the dimension fromside to side of the jam-plate (into and out of the page, as shown withreference to FIG. 9A).

Another alternative, as shown in FIG. 11A, is to have a jam plate 232 beone segment of a hinge, and the hinge be attached through a hinge base233 to a support bushing 226. The free, or unhinged edge 252 of thejam-plate 232 jams into the wall 244 of the lower tube 212, and thehinged end “jams” against the upper tube component 214, by jamming intothe hinge pin 235, which is fixed to the upper component through thehinge base 233 and the bushing 226. As shown in FIGS. 11 and 11A, thehinge can be a simple pinned hinge. Or, as shown in FIG. 11B, it can bea one piece, living hinge 200 fabricated from plastic, metal, or acomposite or other synthetic material. It is even possible to fashionsuch a hinged jam-plate unitarily with an adjacent support bushing,which could further be unitary with a sliding bushing component. Theliving hinge can have virtually no spring constant, or, the hinge motioncan be resisted by a small springiness in the flexible portion of theliving hinge, thereby helping to maintain regularity in the restposition of the jam-plate portion of the hinge.

According to another variation, (as shown in FIGS. 1C and 6C) thesupport bushing 26 can be eliminated. The bushing 26 serves two generalpurposes. One general purpose is to provide a sliding bearing 7, uponwhich the lower component 12 slides with little friction, relative tothe upper component 14. So, regarding this general purpose, the bushingmay be referred to herein as a bearing bushing, or a slide bushing. Thesecond general purpose is to provide support for other elements, such asthe jam-plate and the spring 40. Regarding this general purpose, thebushing may be referred to herein as a support bushing or a jam-platesupport. In some of the embodiments described herein, these generalpurposes are served by multiple individual elements, rather than by abushing.

A support purpose of the bushing is to provide a support, or brace,against which the jam-plate is forced, that is rigidly coupled to theupper leg component 14. This provides a pathway for the jamming force tobe applied to the upper component 14. This function is served by thecorner 46 of the bushing, principally, its circumferential wall.

Thus, in an embodiment without a bushing, the jam-plate must still jamagainst some brace portion of the upper component 14, or an extensionthereof or an element that is rigidly coupled thereto to transmit forceto the upper component 14. (It should be understood that the bushing 26acts essentially as an extension of the upper component 14. Thus, when,in this disclosure, it is stated that the jam-plate jams against theupper leg component 14, it also contemplates that it jams againstsomething rigidly coupled thereto, such as the bushing 26, or anotherelement that is fixed to the upper leg component.) Thus, the uppercomponent 14 can be asymmetrical around its axis of elongation, with anextension 23 around approximately one-half of its arc, extending roughlyto where the end of the bushing 26 would extend, were it present. Asmall ledge 3 can aid in providing a seat into which the edge of thejam-plate can pivot, although, this ledge is not absolutely necessary.

Another support purpose of a support bushing is to keep the jam-platespaced within a certain minimum distance away from the upper component,i.e., to keep the jam-plate from being pushed away from the uppercomponent when the control rod is pushed. This function is served by theupward facing wall 27 of the bushing 26, which prevents the spring 40and the rod 20 from traveling too far downward.

A rib 37, or other brace serves the same support purpose as the back 27of the bushing 26, to engage the spring 40. Even without the supportbushing, it is helpful if a slide bearing 21 is provided, as shown,which, in this case, is in the form of an annular cylinder, having awall length that is longer on one end of a diameter than it is on theother end of the diameter.

Alternatively (not shown), rather than an extension of the upper tubecomponent 14 at the side where the jam-plate contacts it, there can be acut-out of the upper tube component at the side where the jam-platecontacts the lower tube component, with an ear or tab of the jam-plateextending therethrough, to jam against the lower tube wall.

Any of these variations can be achieved, and their usefulness willdepend on the cost and usability considerations. Typically, thosevariations that require fewer components may be less expensive to make,but require more manufacturing precision to ensure ease of use.

Damping of Leg Extension/Collapse. When the jam-plate 32 is in theunlocked position, the upper and lower components 14 and 12 arerelatively free to translate relative to each other. The degree ofresistance to such motion depends on the clearance between the jam-plateand the upper and lower components, as well as any friction, or dampingbetween the upper and lower components themselves, in their region ofoverlap or, more typically, between the components 12 and 14 and theadjacent annular bushings 16 and 26. The designer can provide as much oras little damping as required. The designer can strive for completeclearance at all locations, thus, providing essentially resistance freemotion when the lock is disengaged. Or, the designer can intentionallyprovide for some frictional dragging between either the upper and lowercomponents, or the jam-plate and either or both of the leg components.The designer can intentionally provide explicit damping elements inthese positions, such as the low friction bushings 16, or even pneumaticdampers, such as semi-sealed spaces. For instance, vent holes can beprovided in the upper bushing 28 and the jam seat bushing 26. At leastone of the bushings must block off the air in the leg sufficiently tohave a pumping (displacing) effect on the air when the leg is extended.

It is possible to also provide foam plastic rubber dampers. Also, acombination of springing (at the end of the stroke by a foam rubberspring) and a pneumatic damping, is elegant and robust.

Rather than using a coil spring such as shown at 40, any suitable springcan be used, such as a leaf spring, Belleville washer, or an elastomericblock. The spring can also be positioned in other places. A compressionspring can act against the upper face of the upper bushing 24, or atension spring can act against the bottom face of the upper bushing 24,or against a fitting secured to the upper component in some otherfashion.

Jam-Plate Located within Tubes, Jam between Inner Surfaces of Both. Thejam-plate arrangement discussed above is unusual because it operatesbetween generally facing, inner surfaces of adjacent components, lowerleg component 12 and upper leg component 14. For instance, as shown inFIG. 1C, the jam-plate 32 operates between the face 44 of the lowercomponent 12, and the generally opposite face 25 of the upper component14. To do this, either a portion of one of the components must beremoved, such as part of the lower end 22 of the upper component 14, or,an extending component, such as a support bushing 26 (FIG. 1A) must beprovided that transfers force from one portion of the component toanother. By generally opposite faces, a non-rigorous definition ismeant. For instance, a pair of surfaces that lie at opposite ends of aline that passes through the central axis of the leg, with the centralaxis of the leg being between the faces, are generally opposite faces,as used herein.

Most other instances of jamming type locks operate between an innersurface of a relatively outer component, and an outer surface of arelatively inner component. As such, they operate in a relatively smallspace. This makes it difficult to achieve robust stopping force. Also,it requires that the control mechanism pass in the same small space. Thejam-plate arrangement discussed above can incorporate a relatively largejam-plate 32. Further, the space in which it resides is relativelylarge, being almost equal to the entire interior of the lower component.It is also very useful that the control rod 20 passes through near tothe center of the elongated components, where there is a lot of spacelaterally, thereby facilitating assembly, and permitting relativelyloose tolerances for the control rod support structures. It alsofacilitates a design that can be relatively easily extended to threetelescoping components, as discussed below.

Cross-sectional Shape of Leg Components. The foregoing discussion hasillustrated the concept of the jam lock with leg components of cylindershaving circular cross-sections. This is most likely the most usefulconfiguration, as it is immune to unwanted jamming if the componentsrotate relative to each other. However, cylinders of othercross-sections in which a jam-plate can be placed are possible. (As usedherein, cylinder is not limited to a circular cylinder and is used inits general sense.) For instance, the cross-section could berectangular, particularly square. Additionally, any axially symmetricpolygon having an even or odd number of sides, can be used, such as asquare, a pentagon, a hexagon, an octagon, etc. In such case, jammingaction can be at a flat side or two or more adjacent sides spanning anapex.

In fact, symmetry is not required, and quite a few shapes can be used.If the leg tube has a perimeter shape that could be extruded, then thejam-plate can be roughly of a shape that could be cut from a solidextrusion of that shape, at an angle other than perpendicular to theaxis of extrusion. The shape must then be refined for purposes of theproper clearance, interfacing with a bushing, or undercut slot, or otherfeature. But, the general outline of much of the jam-plate can be soestablished by the obliquely angled cross-section of an extrusion. Forinstance, as shown in the figures, the extruded shape is a circle, andthe jam plate has an outline that is roughly follows a portion of anellipse, a conic cross section of the circular cylinder.

The leg component tube need not be a continuous cylinder. It may be anopen channel, for instance a partial rectangle, with four corners, threecomplete sides, and an interrupted side. In that case, the jam-plate isalso a rectangle, of slightly larger dimensions. Or, it may be aninterrupted circular cylinder, made from a rolled sheet of materialwhose ends do not meet. Such an open channel design leg componentfacilitates access to the internal mechanisms for fabrication, repair,and adjustment (at the cost of allowing access to same by dirt and othercontaminants). There are also other advantages, such as their minimalweight. Basically, any shape that can trap a jam plate will functionproperly, as determined by the person skilled in the art by routineexperimentation.

Legs Can Be Simultaneously Deployed. The discussion so far has centeredon a locking mechanism as used in a single leg. The locking mechanismhas advantages over known prior art. The lock can be engaged simply bydepressing the control rod (as discussed below). Gravity can be used todo the actual extension and collapse. Further, identical jam-plate lockscan be used in each leg of a multi-legged instrument support, mosttypically, a tripod. As is discussed below, it is possible to provide auser interface that activates multiple control members simultaneously,so that all legs (for instance three) of an instrument can be unlockedsimultaneously, and, simultaneously extended or collapsed. For instance,if, in a tripod incorporating such a jam-plate lock, all three controlmembers are simultaneously activated, to release all three locks, thenthe tripod can be un-collapsed by simply activating all of the controlmembers and suspending the tripod with the lower leg componentsdownward. Gravity acts upon the lower leg components, and they extend.

To retract the legs, the control members are simultaneously activated,the legs' lower ends are pushed against the ground or a supportsimultaneously, and, they collapse upward toward the upper legcomponents.

If desired, a preloaded spring, or pneumatic source may be added tofacilitate extension. The preload would most likely be most beneficialif provided to overcome static friction before any relative motion ofthe tube components begins. For instance, a small spring may be providedat the end of the bottom tube component, which provides an initial boostto expanding the leg components from a rest position, but that is easilycompressed upon complete collapse, particularly given the momentum andlow dynamic friction of the moving components. However, then, this mustbe overcome to collapse the unit.

Various user interfaces are suitable for use with the jam-platedescribed above. Several are discussed below.

Unitary Rotary/Tilting User Interface. FIG. 2 shows, schematically, theshoulder portion of a tripod that incorporates a unitary user interfacefor activating control members that are rods, as discussed above. Threeupper leg components 14 are shown. Each has a control rod 20 passingtherethrough, as discussed above. Only one such control rod 20 isvisible, as shown. Each upper component 14 is secured in a suitableupper socket 70, by a suitable means, such as a clamp fitting 72, ormating threads. Each socket is coupled by a hinge 74 to a shoulderbracket 76. For a conventional tripod, the shoulder bracket supports anequipment support tube 78 by conventional means, not shown, such as arack and pinion, that enables lifting and lowering the support tuberelative to the shoulder bracket by a crank. (Some surveying equipmentis mounted directly on a shoulder, without any extended support tube orequipment head. This direct attachment provides enhanced stability.) Thehinges 74 enable closing the legs together to form a compact package, asshown in FIG.3.

A collar 80 is coupled to the shoulder bracket 76 so that it has limitedfreedom to move. The collar has three lobe extensions 82 a, 82 b and 82c. The collar is free to rotate (as indicated by an arrow R) around anaxis V that is aligned with the equipment support tube 78. In onedesign, it is not free to rotate fully around this axis, but onlythrough an arc sufficient to activate the control rods 20, as discussedbelow. A similar design does permit full rotation, as discussed below.In a typical three leg embodiment a rotation through about 5°–40° issufficient. (A preferable range is 10°–20°.) Rotation could be throughas much as 120°, but no more for a three-legged device, as that amountsto ⅓ of the full circumference.

What is required is that the collar be able to rotate enough to actuatethe control rod through two positions, as described below. This motionis referred to below as a “unified control motion.”

The collar 80 is also free to tilt around three intersecting axes, a, band c, which each run generally perpendicular to one of three axes a′,b′, and c′ that run from an intersection point at the center of thecollar, radially outward through a corresponding lobe 82 a, 82 b and 82c. Similarly, the collar is not free to tilt unrestrained around theseaxes but, only through a relatively small angle, which is enough toindividually actuate each of the control rods 20. Further, the presenceof the equipment support bracket 78 also limits the tilting freedom.Generally, it has been found that the tilt angle can be between 5° and40°, and preferably between 15° and 30°. These tilt motions around axesa, b or c are referred to below as “single control” motions.

FIG. 3 shows the same elements as are shown in FIG. 2, from below thecollar, as seen from the legs 10. The control rod 20 a extends fromwithin the upper leg component 14, terminating in a cam follower surface84 a. The cam follower surface presses against the underside 81 of thecollar 80, at a relieved cam profile 86 a, described more fully below.

FIGS. 4A and 4B show the user interface collar 80 from below. Each ofthe three lobes 82 a, 82 b and 82 c (for a three legged version) has acam recess 86 a, 86 b and 86 c, respectively, relieved into theunderside of the lobe 82 x (x=a,b,c). In a preferred embodiment, therecess has a relatively shallow region, 88 s, and a relatively deeperregion 88 d. These regions are also shown schematically with referenceto FIG. 4C, which is a partial cross-section of the lobe 82 c, showing apartial contour of the recess 86 c. FIG. 4D shows this same recess 86 c,with the control rod 20 c, with its cam follower surface 84 c, extendinginto the deeper portion 88 d. FIG. 4E shows this same recess 86 c, withthe control rod 20 c, with its cam follower surface 84 c extending intothe shallower portion 88 d.

The three control rods 20 a, 20 b and 20 c are arranged relative to thethree recesses 86 a, 86 b and 86 c such that if one control rod isextending into the deeper portion of its respective recess, then so willthe other control rods be extending into their corresponding deeperrecess regions. Similarly, if one is extending into the shallower regionof the recess, so will the other two.

Taking the case first where the control rods are all positioned in thedeeper regions 88 d of the respective recesses 86, if the collar 80 isrotated around the axis V to follow the arrow R, each profiled camrecess surface 86 pushes its respective control rod generally away fromthe collar, as the shallower region of the recess is rotated to beadjacent the control rod cam follower surface. Essentially the controlrod cam surface rides up the slope, from the deeper region 88 d to theshallower region 88 s. This motion of the control rod tips thecorresponding jam-plate 32, from the locking position, to the unlockingposition shown in FIG. 1B. Thus, there is no locking force holding thetwo leg components 12 and 14 relatively stationary, and they are free tomove, under the influence of gravity, or pulling by the operator, orunder the influence of a preload within the tube.

When the legs are at their desired relative positions, the collar isrotated back, around the axis V, against the direction of the arrow R,through a unified control motion, allowing the control rods to return tothe deeper portions of the recess, under influence of the return spring40, which allows the jam-plate to return to its jamming position,thereby locking the leg components against relative translation.

There is another way to simultaneously release all of the legs foradjustment. If the collar 80 is pushed down uniformly towards the legs,all of the 88 x (x=a, b and c) surfaces will also move down. (A spring,not shown, statically supports the collar 80 a small distance above thelower limit of its travel aligned with the arrow V.) If the control rodcam follower ends were all in the shallow portion 88 s of theirrespective recesses, then the jam-plate remains unengaged. But even ifthe control rod 20 cam follower ends were all in the deeper portion 88 dof the recess profile, the uniform downward translation of 80 will causeall the control rods 20 to be depressed, thereby releasing all of thejam-locks. In a useful embodiment, there is room for an approximately1.5 cm downward translation that will release the legs. A useful rangefor this motion is between 0.75–2 cm. This action may also be aided witha lever and a cam (not shown).

The foregoing explains simultaneous leg manipulation. It is alsotypically necessary to adjust one or more legs individually. Forinstance, a typical mode of operation would be to simultaneously releaseall three legs and move them to an approximate position together, andthen lock them simultaneously. Then, each leg is individually movedthrough a smaller adjustment to the precise, desired orientation.

To unlock an individual leg, for instance the leg 10 c that isassociated with control rod 20 c, the collar 80 is tilted through asingle control motion around the axis c, toward the leg 10 c. This tiltforces the control rod 20 c downward, but does not force the other twocontrol rods at all (or, if at all, not enough to change the orientationof the jam-plate). Forcing the control rod 20 c downward releases thecorresponding jam-plate 32, as described above, so that the upper andlower leg components of the leg 10 c can be translated relative to eachother. When the collar 80 is un-tilted, back to a neutral orientation,the jam-plate 32 returns to its jamming orientation, and the legcomponents lock together.

Each leg can thus be unlocked and adjusted individually, simply bytilting the user control collar 80 through a single control motionaround the appropriate axis a, b or c, toward the leg to be adjusted. Ingeneral, an appropriate axis is one that is roughly perpendicular to anaxis that is generally radial, from the center of the collar, outwardtoward the axis of elongation of the leg to be adjusted.

For instance, as shown in FIG. 2, tilting the collar around the axis areleases the jam-plate for the leg 10 a. This axis is also locatedbetween the central axis of the collar, V and the point at which the camfollower of the control rod 20 c contacts the cam recess 86 c. Thus, asshown in FIG. 2, tilting the collar around the axis a releases thejam-plate for the leg 10 a; tilting the collar around the axis breleases the jam-plate for the leg 10 b; and tilting the collar aroundthe axis c releases the jam-plate for the leg 10 c.

Of course, there might also be situations where the user opts to adjusteach leg individually, and not to adjust all of the legs simultaneously.The described inventions also make this mode of operation very simple.

The foregoing has described an apparatus where relaxation of a jam-platein a given leg is achieved by tilting of the control collar through asingle control motion toward the leg to be adjusted. A variation is,perhaps, not quite as intuitive. Instead, to achieve relaxation of ajam-plate in a given leg, the collar is tilted through a single controlmotion around a radial axis that is perpendicular to the axis mentionedabove. For instance as shown at a′ in FIGS. 2 and 3, to relax the leg 10a, nearest to the lobe 82 a, the collar is tilted around the generallyradial axis a′. This may not be as intuitive for some operators, as theembodiment discussed above, because the lobe is not tipped toward theleg to be adjusted, but rather is tipped around an axis that passesthrough the leg to be adjusted. Although perhaps not as intuitive, thisvariation may be easier to implement, and is still rather intuitive andcan be easily learned. Either variation works equally well from astandpoint of the control rod and recess relationship.

Rather than individual pocket recess profiles 86, with two depths, it isalso possible to provide a continuous wave profiled cam 286, with twomajor levels, with a third, border level interposed therebetween, asshown schematically in FIG. 4F. This profile 286 is continuous, aroundthe entire circumference of the collar. In such a case, the rotationaltravel of the user interface collar 280 for the unified control motionneed not be limited to (360° divided by the number of legs), but rathercan be continuously rotated beyond 360°. Further, rather than reversingrotation to return to a locked status, rotation can simply be continuedin a forward direction R, to the next deep trough 288 d (or shallowtrough 288 s as the case may be) in the wave profile 286. The profile isthus wave-like, as shown in FIG. 4F. The deep troughs 288 d correspondto the deeper portion 88 d of the recess 86 described above, and theshallower trough 288 s correspond to the shallower portion 88 s of therecess 86. The small crests 289 prevent inadvertent slipping of thecollar from a shallower, unlock trough 288 s to a deeper, lock positiontrough 288 d and also the reverse.

From the foregoing, it is evident that the user interface collarprovides an elegant, unitary, robust way for a user to adjust the legseither simultaneously, or individually, simply by manipulating one userinterface element, through simple, well-defined, operationally distinctmovements. The user need not look for small latches, or move his or herhand from one locking mechanism associated with one leg, to another,associated with another leg. Nor need the user move the hand from onelocking mechanism associated with a single leg, to another associatedwith all of the legs. Moreover, all necessary operations can beconducted with one hand, without looking. The user must simply grasp asingle, relatively large, easy to blindly locate, element, andmanipulate it through simple motions. The motions are, a unified controlrotation motion around one axis for simultaneous deployment/collapse,and single control tilting motions around one of three individual axesfor individual adjustment.

Other Shapes for the User Interface. Rather than being relativelyplanar, as shown, the collar can be more pyramidal shaped, with its apexaligned along the axis V. Such a user interface 380 is shownschematically in FIGS. 10A and 10B. Such a collar 380 may have a partsimilar to the planar element 80 embedded within it, or, its undersurface 381 may be identical to the undersurface 81 of the userinterface collar 80 described above. However, the variation may providemore volume to provide an even larger surface for grabbing andmanipulating the collar. For example, with gloved hands, the larger,more voluminous collar might be preferred. The lobes 382 a, 382 b and382 c are easily grasped. Tactile or visual indicia 383 may be providedto enhance user recognition of the lobes.

Or, rather than being continuous, its lobes can be more separated, suchas radiating fingers. All that is required is that there must be aportion of the interface that is wide enough to allow space for the deepand shallow portions of the cam recess.

It will also be understood that for a tripod, rather than a lobedcollar, as shown, a simple triangular collar can be used, with a vertex,or a side of the triangle, being aligned with a leg of the tripod.

The profile of the control recess can be different, as long as itpermits appropriately changing the location of the push rod or othercontrol member when the collar is rotated and tilted.

Multiple Legs, other than Tripods. Most equipment supports are tripods,or, monopods. However, in some cases, supports with more than three legsare used. For instance, some surveying equipment supports have more thanthree legs. The jam lock and the unitary user interface collar discussedabove can be used with such stands of higher leg number. In such a case,the collar has a shape that is convenient to use with the higher numberof legs. It may have a shape that provides a lobe for each leg. Or,rather than lobes, regular polygonal shapes, such as pentagons,hexagons, octagons, etc. can be used. Or, stars with the requisitenumber of points can be used.

Alternatively, the collar can be hemispherical, or, another smooth,regular shape. It still has the tilting and rotating capability asdescribed above, with profiled recesses, but without the lobes. Thedesign is intuitive enough not to require the lobes to indicate whichmotion adjusts which leg. Alternative to lobes, a smoothly shaped collarcan have visual, or tactile indicia as indicated at 383 in FIG. 10B,located adjacent the legs, such as brightly colored marks, raisedpatterns, or indentations.

Three Leg Component Design. The foregoing discussion describestwo-component legs, having an upper and a lower component. FIG. 7 showsthat a similar concept can be used in connection with a three-componentleg, having a middle component 113 that is between an upper 114 and alower 112 component. Such an arrangement is shown schematically, incross-section, in FIG. 7. For each three component leg, there are threecontrol rods: a primary control rod 120 and a set of two secondarycontrol rods 121 a and 121 b. (One of these secondary control rods isnot strictly necessary, but, is for redundancy in case one of the rodsslips.)

The primary control rod 120 extends to a user interface collar (notshown) in generally the same manner as does the control rod 20,described above for a two component leg. (A difference is that, asexplained below, pushing the control rod 120 downward in the directionof the arrow L, (toward the jam-plates 131 and 132), locks thejam-plates, while, in the two component design discussed above, pushingthe control rod 20 downward unlocks the jam-lock.

For each three component leg, there are two jam-plates: a primaryjam-plate 131, and a secondary jam-plate 132. An primary support plate127 is fixed to the lower end of the upper component 114. A secondarysupport plate 129 is fitted to the lower end of the intermediate legcomponent 113. A primary jam-plate pivot 133 is also fixed to the upperleg component 114. As shown, this primary pivot is fixed to an extension125 of the primary support plate 127. Alternatively, it could be fixedto an extension of the upper tube component 114 itself. The pivot 133pivotally supports the primary jam-plate 131, so that the jam-plate 131is free to pivot around the pivot point.

The primary control rod 120 passes through an opening 123 in the primarysupport plate 127. The secondary control rods 121 a and 121 b passthrough openings 137 a and 137 b in the secondary support plate 129. Asecondary jam-plate pivot 135 is fixed to the lower, intermediatecomponent 113. As shown, this secondary pivot is fixed to an extension139 of the secondary support plate 129. Alternatively, it could be fixedto an extension of the intermediate tube component 113 itself. The pivotpivotally supports the secondary jam-plate 132, so that the jam-plate132 is free to pivot around the pivot point.

An upper annular bushing 141 is fixed to the upper end of theintermediate tube component 113 and another bushing 151 at the lower endof the upper tube component 114, and permits the two tube components toslide relative to each other, with relatively little friction, or wear.The bushing is made of a low friction, wear resistant material.Similarly, bushings 143 and 153 are fixed to the upper end of the lowertube component 112 and the lower end of the intermediate tube component113.

The configuration shown in FIG. 7 is an unlocked configuration. In thisconfiguration, the lower tube component 112 is free to translaterelative to the intermediate component 113. If it does, then it alsotranslates relative to all of the other elements shown in FIG. 7(except, the bushing 143, which is fixed to the lower component 112).The intermediate tube 113 is also free to translate relative to theupper tube component 114. If it does, then the secondary support plate129 also translates, as does the pivot 135, and the secondary jam-plate132, as well as the secondary control rods 121 a and 121 b. The controlrods 121 a and 121 b are free to translate relative to the primary jamplate 131 and the upper tube component 114, because the secondarycontrol rods pass freely through the openings 143 a and 143 b in theprimary jam-plate 131.

To lock the jam-plates, the user pushes the primary control rod 120downward (toward the jam-plates), by means of a collar, similar to thatdescribed above, with profiled recesses. Pushing down on the primarycontrol rod 120 in the direction of the arrow L_(p) pushes downward onone side of the primary jam-plate 131, relative to the primary pivot133, causing the primary jam-plate to pivot around the pivot point 133,counter-clockwise, as shown. This causes the other side of the primaryjam plate to move upward, relative to the pivot point 133, as indicatedby the arrow U_(p). Moving upward, the edge _(152p) of the primaryjam-plate 131 eventually contacts the inner surface 145 of theintermediate leg component 113, causing a jam-lock, as described above.

The flow of force is from the intermediate component 113 sidewall 145 tothe edge 152 _(p) of the primary jam-plate 131, through the pivot point133, to the upper tube component 114 through either the extension 125 ofthe primary support plate 127, and the support plate itself, or, throughan extension of the upper tube component 114 (not shown for thisvariation).

Tilting of the primary jam-plate (in a counterclockwise direction, asshown) eventually tilts enough to trap the secondary control rods 121 aand 121 b in the openings 143 a and 143 b of the primary jam-plate 131,which then drives the secondary control rods 121 a and 121 b along thedirections of the arrows La_(s) and Lb_(s) respectively, shown, to alsotilt the secondary jam-plate 132 around the pivot point 135 in acounter-clockwise direction, as shown. This tilting of the secondary jamplate 132 also causes it's edge 152 _(s) to tilt upward following thearrow U_(s) so that the secondary jam-plate 132 jams against the innersurface 147 of the lower tube component 112, thereby jam locking againstit.

The clearance between the secondary control rods 121 a and 121 b and theprimary jam-plate 131 must be large enough to permit the control rods toslide through when the leg components are being collapsed, but alsosmall enough to ensure that when the primary control rod 120 isdepressed, the secondary control rods are captured by the tiltedjam-plate 131 and thus non-parallel channels 143 a and 143 b, withenough friction to be pushed and pulled as indicated, to tilt and jamthe lower jam-plate 132.)

Thus, it is again the case that the jam-lock prevents the leg componentsfrom collapsing to a closed configuration, under the influence of a loadupon the legs as would be generated by equipment supported at the upperend, with the lower legs resting on the ground. Such a load tends tofurther jam the jam-plates 131 and 132 into a jamming configuration, andthus, to lock them more securely.

The leg is locked by pushing the primary control rod 120 downward. Thisis accomplished in the same manner as described above, with a camfollower surface at the upper end of the primary control rod 120, and aprofiled recess under a user interface collar. When forced into ashallower portion of a cam profile, the rod is forced downward, andcauses the jamming action. (It should be noted that the embodimentsdiscussed above effect unlocking, with pushing the control rod, whilethis embodiment effect locking, with pushing of a control rod.)

To unlock the jam-plates, the collar is turned so that the cam followeris adjacent a deeper region of the cam profile, so that the control rod120 is free to snap back into the deeper region. The primary control rodis urged to snap back in that direction (against the arrow L_(p) asshown in FIG. 7) under influence of the primary return spring 140 _(p)and secondary return springs 140 _(sa) and 140 _(sb).

Thus, both the primary and the secondary jam-plates are locked, andunlocked substantially simultaneously. Thus, a leg can be completelyextended, or collapsed when the jam-plates are in the unlockedconfiguration.

Further, to adjust a single leg, a similar action can be applied as usedwith the two-component design discussed above. However, in this case,the collar is tilted away from the leg to be adjusted, rather thantoward it. In other words, the portion of the collar adjacent the leg tobe adjusted is tilted upward, and downward opposite it, between theother two legs to be left unadjusted. This also puts additional downwardpressure on the two primary control rods associated with the two legsthat are not to be adjusted. In that case, the collar has a form thatfacilitates lifting upward. The lobes shown certainly are equallysuitable for lifting upward as for pushing downward. Other shapes arealso suitable.

In this embodiment, the support functions and the bearing functions areentirely separate. The support functions are taken by the primary andsecondary supports 131 and 132, and the bearing functions are taken bythe bushings 141, 143, 151 and 153.

When the components of this three-component leg design are collapsed,they form a relatively compact package. The lower component 112 fitsentirely around the intermediate component 113. The intermediatecomponent walls fit around the walls of the upper component 114. Theprimary jam-plate is substantially fixed relative to the uppercomponent, except for its freedom to tilt. Thus, when the unit iscollapsed, the primary jam-plate 131 remains relatively fixed. Thesecondary jam-plate 132 and the secondary support 129 are substantiallyfixed relative to the intermediate component 113, and as it movesupward, toward the upward component 114, so do they. Similarly thesecondary control rods 121 a and 121 b move with the secondary jam-plate132, and thus, with the intermediate component 113. Their upper endspass through channels in the upper support 127.

Additional Embodiments. Rather than push rods, spring loaded tensionelements such as cables, or straps, that are pulled, rather than pushed,may be used. In such a case, typically, an upward tipping motion wouldrelease the lock, rather than a downward pushing motion. Such devicescould be lighter than those with push rods, as the tension elementscould be made of material that is lighter than that used for compressionbearing, pushable control rods. Thus, when the term control member isused herein, it is used to mean any such control member, which can bepushed, like a rod, or pulled, like a cable.

In very rare cases, an equipment support might be suspended from anoverhead support, rather than being supported by the ground, or othergrounded fixture. In that case, the support would hang from the leg orlegs, and the equipment would hang from the shoulder, rather thanbearing down upon it. The inventions disclosed herein can be used inthat context. However, the orientation of the jam-plate must bereversed, because it must oppose a force that would tend to separate themultiple leg components from each other. In the conventionalconfiguration, described above, the jam-plate is arranged to resist aforce that would tend to collapse the multiple leg components towardeach other. It is also possible to provide equipment with removablejam-plate cartridges, which can be reversed, to use in the invertedconfiguration, or swapped with an inverted orientation jam-platecartridge. Or, dual jam-plates can be used, one of which is configuredto be active only when the load is applied to compress theleg-components, and the other to be active only when the load is appliedto extend the leg-components.

Many techniques and aspects of the inventions have been describedherein. The person skilled in the art will understand that many of thesetechniques can be used with other disclosed techniques, even if theyhave not been specifically described in use together.

This disclosure describes and discloses more than one invention. Theinventions are set forth in the claims of this and related documents,not only as filed, but also as developed during prosecution of anypatent application based on this disclosure. The inventors intend toclaim all of the various inventions to the limits permitted by the priorart, as it is subsequently determined to be. No feature described hereinis essential to each invention discloed herein, but not claimed in anyparticular claim of any patent based on this disclosure, should beincorporated into ant such claim.

Some assemblies of hardware, or groups of steps, are referred to hereinas an invention. However, this is not an admission that any suchassemblies or groups are necessarily patentably distinct inventions,particularly as contemplated by laws and regulations regarding thenumber of inventions that will be examined in one patent application, orunity of invention. It is intended to be a short way of saying anembodiment of an invention.

An abstract is submitted herewith. It is emphasized that this abstractis being provided to comply with the rule requiring an abstract thatwill allow examiners and other searchers to quickly ascertain thesubject matter of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims, as promised by the Patent Office's rule.

The foregoing discussion should be understood as illustrative and shouldnot be considered to be limiting in any sense. While the inventions havebeen particularly shown and described with references to preferredembodiments thereof, it will be understood by those skilled in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the inventions as defined by theclaims.

The corresponding structures, materials, acts and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or acts for performing the functions incombination with other claimed elements as specifically claimed.

1. A multi-legged equipment stand comprising: a. a shoulder bracket; b.coupled to said shoulder bracket, a plurality of telescoping, elongatedlegs, each leg having an uppermost elongated component and a lowerelongated component, said uppermost and lower components being elongatedalong an axis of elongation, said uppermost elongated component beingtranslationally fixed relative to said shoulder bracket, and said lowerelongated component being translatable relative to said shoulder bracketand said uppermost component, along said axis of elongation, saiduppermost component having a shoulder end, and a ground end, said lowercomponent having a shoulder end and a ground end, said shoulder end ofsaid uppermost and lower components being located nearer to saidshoulder bracket than said ground end of said respective components; c.for each pair of uppermost and lower components of a leg, a releasablelock that engages both said uppermost and lower components, said lockbeing movable from a locking configuration that contacts both of saiduppermost and lower components and locks them to prevent relativetranslation thereof, to a non-locking configuration, in which saidcomponents are substantially freely translatable relative to each other;d. coupled to each of said lock, a control rod, which extends from saidlock, along said uppermost elongated component to adjacent said shoulderbracket, terminating in a cam follower surface, and which rod is coupledto said lock to selectively lock or unlock said lock if said control rodis moved; e. a user interface element, supported by said shoulderbracket, adjacent said cam follower surfaces of said plurality ofcontrol rods, said user interface element comprising a profiled camrecess surface; f. a couple between said shoulder bracket and said userinterface collar, which partially restrains said user interface elementsuch that: i. a unified control motion of said user interface elementrelative to said support simultaneously moves all of said control rodsso that all of said locks are unlocked; ii. a first single controlmotion of said user interface element relative to said shoulder bracketmoves only a first one of said control rods so that a corresponding oneof said locks is unlocked, while simultaneously, all others of saidlocks are unaffected with respect to their respective lock state; andiii. a second single control motion of said user interface elementrelative to said shoulder bracket moves only a different, second one ofsaid control rods so that a corresponding one of said locks is unlocked,while simultaneously, all others of said locks are unaffected withrespect to their respective lock state.
 2. The equipment stand of claim1, said plurality of legs comprising three.
 3. The equipment stand ofclaim 1, said lock comprising a spring loaded jam-plate.
 4. Theequipment stand of claim 3, said uppermost and lower elongated legcomponents comprising hollow tubes, with said lower component arrangedconcentric with and outside of said uppermost component, said jam-platearranged to jam against an inner surface of said lower elongatedcomponent and against said uppermost elongated component.
 5. Theequipment stand of claim 4, said jam-plate arranged to jam against aninner surface of said uppermost elongated component.
 6. The equipmentstand of claim 4, further comprising a support bushing fixed to saidground end of said uppermost leg component, said jam-plate arranged tojam against said uppermost elongated component by jamming against saidsupport bushing.
 7. The equipment stand of claim 6, said jam-platecomprising a hinged jam-plate that is hinged to said support bushing. 8.The equipment stand of claim 7, said hinged jam-plate comprising apinned hinge.
 9. The equipment stand of claim 7, said hinged jam-platecomprising a living hinge.
 10. The equipment stand of claim 6, saidsupport bushing having a slotted surface, said jam-plate comprising aplate having an edge with a tab that is sized and shaped to fit withinsaid slot.
 11. The equipment stand of claim 3, said uppermost and lowerelongated leg components comprising hollow tubes, with said lowercomponent arranged concentric with and outside of said uppermostcomponent, said jam-plate arranged to apply a force that has a radiallyoutward component against each of an inner surface of said uppermost legcomponent and an inner surface of said lower leg component.
 12. Theequipment stand of claim 11, said inner surfaces of said upper most legcomponent and of said lower leg component being arranged generallyfacing each other.
 13. The equipment stand of claim 3, said uppermostand lower elongated leg components comprising hollow tubes, with saidlower component arranged concentric with and outside of said uppermostcomponent, said control rod comprising a rod that passes along theinside of both said uppermost and lower hollow tube components.
 14. Theequipment stand of claim 3, said user interface element comprising, aprofiled cam surface shaped to simultaneously force each of said controlrods away from said user interface element if said user interfaceelement is rotated around said unified control axis, and, individuallyforce a single control rod away from said user interface element if saiduser interface element is tilted around a single control axis associatedwith said respective single control rod.
 15. The equipment stand ofclaim 14, said cam profile surfaces comprising, for each control rod, atwo level well, with a sloped profiled region joining said two levels.16. The equipment stand of claim 14, said cam profile surfacecomprising, a continuous 360° wave profile having at least two levels ina repeating pattern around the circumference of the user controlelement.
 17. The equipment stand of claim 1, said user interface elementcomprising a collar, said unified control motion comprising rotationaround a unified control axis, said first single control motioncomprising tilt around a first, single control axis and said secondsingle control motion comprising tilt around a second, single controlaxis.
 18. The equipment stand of claim 17, said single control axeslying in a plane that is perpendicular to said unified control axis. 19.The equipment stand of claim 1, said leg components comprisingcylindrical tubes, and said lock comprising a jam-plate having at leastone arcuate curved edge.
 20. The equipment stand of claim 1, saidplurality of legs comprising three legs, said user interface elementcomprising a unitary, three-lobed collar, which controls both unifiedmotion of said control rods, and single control motion of said controlrods.
 21. The equipment stand of claim 20, said three lobed collarcomprising a substantially planar collar.
 22. The equipment stand ofclaim 20, said three lobed collar comprising a substantially dome shapedcollar.
 23. The equipment stand of claim 1, said unified control motioncomprising a motion that substantially simultaneously forces saidcontrol rods toward said ground ends of said legs.
 24. The equipmentstand of claim 1, said first single control motion comprising a motionthat forces said respective control rod toward said ground end of saidlegs.
 25. The equipment stand of claim 1, said unified control motioncomprising a motion that substantially simultaneously forces saidcontrol rods toward said shoulder ends of said legs.
 26. The equipmentstand of claim 1, said single control motion comprising a motion thatforces said respective control rod toward said shoulder end of saidlegs.
 27. A multi-legged equipment stand comprising: a. a shoulderbracket; b. coupled to said shoulder bracket, a plurality oftelescoping, elongated legs, each leg having an uppermost elongatedcomponent and a lower elongated component, said uppermost and lowercomponents being elongated along an axis of elongation, said uppermostelongated component being translationally fixed relative to saidshoulder bracket, and said lower elongated component being translatablerelative to said shoulder bracket and said uppermost component, alongsaid axis of elongation, said uppermost component having a shoulder end,and a ground end, said lower component having a shoulder end and aground end, said shoulder end of said uppermost and lower componentsbeing located nearer to said shoulder bracket than said ground end ofsaid respective components; c. for each pair of uppermost and lowercomponents of a leg, a releasable lock that engages both said uppermostand lower components, said lock being movable from a lockingconfiguration that contacts both of said uppermost and lower componentsand locks them to prevent relative translation thereof, to a non-lockingconfiguration, in which said components are substantially freelytranslatable relative to each other; d. coupled to each of said lock, acontrol member, which extends from said lock, along said uppermostelongated component to adjacent said shoulder bracket, terminating in acontrol component; e. a user interface element, supported by saidshoulder bracket, adjacent said control components of said plurality ofcontrol members, said user interface element comprising, for each ofsaid control components, a control activation element and which controlmember is coupled to said lock to selectively lock or unlock said lockif said control mechanism is moved; f. a couple between said shoulderbracket and said user interface element, which partially restrains saiduser interface element such that: i. a unified control motion of saiduser interface element relative to said support simultaneously moves allof said control members so that all of said locks are unlocked; ii. afirst single control motion of said user interface element relative tosaid shoulder bracket moves only a first one of said control members sothat a corresponding one of said locks is unlocked, whilesimultaneously, all others of said locks are unaffected with respect totheir respective lock state; and iii. a second single control motion ofsaid user interface element relative to said shoulder bracket moves onlya different, second one of said control members so that a correspondingone of said locks is unlocked, while simultaneously, all others of saidlocks are unaffected with respect to their respective lock state. 28.The equipment stand of claim 27, said control member comprising a rodthat is capable of bearing compression and tension.
 29. The equipmentstand of claim 27, said control member comprising a cable that iscapable of bearing tension.
 30. The equipment stand of claim 27, saidcontrol member comprising a linkage that is capable of bearingcompression.
 31. The equipment stand of claim 27, said control membercomprising a linkage that is capable of bearing tension.
 32. Theequipment stand of claim 27, said couple between said shoulder bracketand said user interface element, partially restraining said userinterface element such that said first single control motion of saiduser interface element relative to said shoulder bracket moves only afirst one of said control members so that a corresponding one of saidlocks is unlocked, while simultaneously, all others of said locks remainlocked.
 33. An equipment stand comprising: a. at least three telescopinglegs, each leg comprising at least two telescoping components; b. asingle, unitary control user contact member, operative to selectivelyperform one of the following release functions: i. release all of saidlegs for telescoping adjustment between said at least two telescopingcomponents; and ii. release only a selected one of said legs fortelescoping adjustment between said at least two telescoping componentsof said one leg, while, simultaneously maintaining all others of saidlegs locked against adjustment between said at least two telescopingcomponents of said other legs.
 34. The equipment stand of claim 33, saidstand comprising a tripod.
 35. The equipment stand of claim 34, saidlegs comprising open sided telescoping channel elements.
 36. Theequipment stand of claim 33, said legs comprising telescopingcylindrical tube.
 37. The equipment stand of claim 36, said cylindricaltubes comprising circular cylinders.
 38. The equipment stand of claim 33further comprising, for each leg, a lock and a control linkage, saidlock operative to selectively lock said two telescoping componentsagainst relative motion, and to free them for relative motion, and saidcontrol linkage arranged to couple said lock to said user contactmember.
 39. The equipment stand of claim 33, said unitary control usercontact member comprising a collar, that is rotatable around a unifiedmotion axis to release all of said legs for telescoping adjustment. 40.The equipment stand of claim 39, said collar being further tiltablearound: a. a first single motion axis to release a first of said legsfor telescoping adjustment; b. a second single motion axis to release asecond of said legs for telescoping adjustment; and c. a third singlemotion axis to release a third of said legs for telescoping adjustment.41. The equipment stand of claim 40, said first and second single motionaxes intersecting at a first intersection point, said second and thirdsingle motion axes intersecting at a second intersection point, and saidthird and first single motion axes intersecting at a third intersectionpoint, said first, second and third intersection points forming verticesof a triangle having a centroid through which said unified motion axisruns.
 42. The equipment stand of claim 40, said first, second and thirdsingle motion axes all intersecting at a single point.
 43. A lockingtelescoping leg mechanism, comprising: a. an uppermost elongated hollowtubular leg component, having an inside surface and an outside surface;and b. a lower elongated leg component, having an inside surface and anoutside surface, said uppermost and lower components being elongatedalong an axis of elongation, said uppermost and lower elongated legcomponents being translatable relative to each other, along said axis ofelongation, said uppermost component having a shoulder end, and a groundend, said lower component having a shoulder end and a ground end, saidshoulder end of said lower component being located nearer to saidshoulder end of said uppermost component than is said ground end of saidlower component; c. a releasable jam-plate that engages both saiduppermost and lower components, said jam-plate being movable between: i.a locking configuration that applies a generally radially outward forceto: A. said inside surface of said uppermost component; and B. saidinside surface of said lower component; and ii. a non-lockingconfiguration, in which at least one of said radial outward forces is sosmall that said components are substantially freely movable relative toeach other; and d. coupled to said jam-plate, a control member, whichextends from said jam-plate, inside said uppermost elongated componentthrough substantially its entire length, to adjacent said shoulder end,terminating in a shoulder end, said control member being coupled to saidjam-plate such that motion of said control member moves said jam-platefrom said locking configuration to said non-locking configuration. 44.The leg of claim 43, further comprising, coupled to said control member,a spring, which forces said control member toward a rest position, whichcorresponds to said locking configuration of said jam-plate.
 45. The legof claim 44, said inside surface of said uppermost component said insidesurface of said lower component comprising generally facing surfaces.46. The leg of claim 45, one of said inside surface of said uppermostcomponent said inside surface of said lower component comprising asurface of an axially assymetric extension of said respective legcomponent.
 47. The leg of claim 44, said jam-plate arranged such that insaid locking configuration, said jam-plate constitutes a portion of acontinuous force path from said lower elongated leg component to saidupper elongated leg component.
 48. The leg of claim 43, said jam-platearranged relative to said upper leg component to apply a force directlyto said upper component when said jam-plate is in said lockingconfiguration.
 49. The leg of claim 43, further comprising, secured tosaid ground end of said upper leg component, a jam-plate support, saidjam-plate arranged relative to said support and said upper leg componentto apply a force indirectly to said upper leg component when saidjam-plate is in said locking configuration, by applying a force directlyto said jam-plate support.
 50. The leg of claim 49, said jam-platesupport comprising a support bushing.
 51. The leg of claim 49, saidjam-plate support comprising a surface with a slot, and said jam-platecomprising a plate having an edge that is sized and shaped to fit intosaid slot.
 52. The leg of claim 49, said jam-plate support comprising abushing with a support surface.
 53. The leg of claim 44, said jam-platearranged such that in said non-locking configuration, said jam-plate ismoved such that said force path from said lower elongated leg componentto said upper elongated leg component is discontinuous at saidjam-plate.